title: First evidence of protein G-binding protein in the most primitive vertebrate: serum lectin from lamprey (Lampetra japonica).
abstract: The intelectins, a recently identified subgroup of extracellular animal lectins, are glycan-binding receptors that recognize glycan epitopes on foreign pathogens in host systems. Here, we have described NPGBP (novel protein G-binding protein), a novel serum lectin found in the lamprey, Lampetra japonica. RT-PCR yielded a 1005 bp cDNA sequence from the lamprey liver encoding a 334 amino acid secretory protein with homology to mammalian and aquatic organism intelectins. Gene expression analyses showed that the NPGBP gene was expressed in the blood, intestines, kidney, heart, gill, liver, adipose tissue and gonads. NPGBP was isolated by protein G-conjugated agarose immunoprecipitation, and SDS-PAGE analyses showed that NPGBP migrated as a specific band (∼35 and ∼124 kDa under reducing and non-reducing conditions, respectively). These results suggested that NPGBP forms monomers and tetramers. NPGBP gene expression was induced by in vivo bacterial stimulation, and NPGBP showed different agglutination activities against pathogenic Gram-positive bacteria, Gram-negative bacteria and fungi. The induction of NPGBP suggested that it plays an important role in defense against microorganisms in the internal circulation system of the lamprey. When incubated with an unrelated antibody, the specific binding between NPGBP and protein G was competitively inhibited, indicating that NPGBP and the Fc region of Ig bind to the same site on protein G. We thus assume that the tertiary structure of NPGBP is similar to that of the Fc region of Ig. Additionally, NPGBP can effectively promote endothelial cell mitosis. These findings suggest that NPGBP plays a role in the immune defense against microorganisms, and this study represents one of the few examples of the characterization and functional analysis of an aquatic organism intelectin.
authors.affiliation: Institute of Marine Genomics and Proteomics, Liaoning Normal University, Dalian 116029, China; School of Life Science, Liaoning Normal University, Dalian 116029, China.
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Xue
authors.forename: Yue
authors.initials: Y
authors.lastname: Pang
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zheng
authors.forename: Rong
authors.initials: R
authors.lastname: Xiao
authors.forename: Minli
authors.initials: M
authors.lastname: Jin
authors.forename: Yinglun
authors.initials: Y
authors.lastname: Han
authors.forename: Peng
authors.initials: P
authors.lastname: Su
authors.forename: Li
authors.initials: L
authors.lastname: Lv
authors.forename: Jihong
authors.initials: J
authors.lastname: Wang
authors.forename: QingWei
authors.initials: Q
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins; D042783:Endothelial Cells / Q000276:immunology / Q000382:microbiology; D005658:Fungi / Q000276:immunology; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000276:immunology; D006090:Gram-Negative Bacteria / Q000276:immunology; D016905:Gram-Negative Bacterial Infections / Q000276:immunology; D006094:Gram-Positive Bacteria / Q000276:immunology; D016908:Gram-Positive Bacterial Infections / Q000276:immunology; D007798:Lampreys / Q000235:genetics* / Q000276:immunology; D037102:Lectins / Q000235:genetics* / Q000276:immunology; D008938:Mitosis / Q000276:immunology; D008969:Molecular Sequence Data; D009181:Mycoses / Q000276:immunology; D016415:Sequence Alignment; D014714:Vertebrates / Q000235:genetics* / Q000276:immunology
chemical_list: D002352:Carrier Proteins; D037102:Lectins; D019204:GTP-Binding Proteins
keywords: Agglutination activity; Immune defense; Intelectin; Lamprey; Protein G target